The present invention relates to scanning-oscillators, and more particularly to scanning-oscillator control-systems.
Scanning-oscillator devices have diverse application in fields including communications and signal processing, and find particular utility in compressive-receivers and pulse-compression radar systems.
A scanning-oscillator device is a frequency generator whose output-signal frequency is continuously varied over a particular frequency range as a function of time, as controlled by a scanning-oscillator controller. It is often important to have the output-signal frequency change at a constant, or linear, rate. Implementation of this linear sweep rate has been the subject of various prior designs. The prior attempts demonstrate that indeed it previously has been both difficult and costly to produce a scanning-oscillator having a highly accurate output-signal frequency characteristic and having an output-signal frequency variable in a highly linear fashion. Another major problem related to control of a scanning oscillator is one of not knowing how accurately the oscillator is performing while operating.
The present invention overcomes the prior disadvantages. An embodiment of the present invention accurately determines the amount of deviation of the output-signal frequency from the desired frequency, as well as providing an error-magnitude signal to the oscillator-controller indicating to what extent to alter or adjust the sweep rate.
It is therefore an object of the present invention to control a scanning frequency oscillator so as to minimize the difference between the scanning-oscillator output signal-frequency and a desired output signal-frequency.
It is a still further object of the present invention to control a frequency scanning-oscillator by comparing the time the oscillator output frequency reaches a particular reference-frequency with the desired time that the oscillator signal would be at the particular reference-frequency.